Spitfire Mk.XIV vs P-51D Mustang

[the lancaster kicks ass]

and you could carry more .303 ammo than .50cal.............

Originally Posted by Soren

Yes in their own right they are, and coupled with the 2xHispano's they were very effective. But i wasnt suggesting 8x.303's vs 4x.50's !

So you are suggesting that somehow by being paired with 20mm they become more effective?

Originally Posted by Soren

As far as I remember, you mentioned the .303 to have an ROF of 1200rpm ! and the M2 950rpm.

My error - I should have looked up the RoF rather than rely on memory, where I rounded it to 1200 rpm.

Originally Posted by Soren

The .50 cal round itself was about 4.2-4.6 times as destructive as the .303.

http://www.quarry.nildram.co.uk/WW2guneffect.htm

Tony William's uses momentum, rather than ke, to determine hitting power. Even he admits this is a somewhat arbitrary decision. While I would agree with him that ke is not entirely valid, I also think that momentum is not entirely valid either. Something in between makes more sense, as momentum relates to penetration but ke relates to shock effect and shrapnel/spalling effect. When I did my gun tables, I used the formula:

hitting power = 1/2 mass * velocity^1.6 (i.e raised to the 1.6 power)

This formula splits the difference between momentum and ke results almost exactly in the middle.

Furthermore, they relay the power at the muzzle, not the power at the hitting distance. As I showed before, the .303 velocity drops three times as fast as the .50 velocity for a given target distance.

Originally Posted by Soren

Look at table 2 :GUN POWER AND EFFICIENCY.

Here the Browning .303 and 50 Browning M2 are listed as equal !

This table relates the weight of the gun (but not the ammo supply) to the power in the eariler table. Weight of the gun has nothing to do with effectiveness of the hits, so this table is of no real value.

Originally Posted by Soren

Then take a look at table 3: FIGHTER FIREPOWER.

The Spit Mk.Vc with 4x.303's + 2xHispano's; Armament power= 480.

The Spit Mk.XIV.E with 2x50's + 2xHispano's; Armament power= 520.

They are very close !

Again, that table is based upon the power figures he used earlier, which use muzzle momentum, not really a valid comparison at all.

The problem with the .303's is that by the time they've pentrated the skin they have little power left. They tumble easily too and don't have enough mass to penetrate well even with a perpendicular strike, a strike while oriented sideways will do little damage to most components and almost none to structure. The .50's are large enough and have enough mass/energy to penetrate the skin and do damage to anything they hit inside, even if they tumble - in fact usually they would do more damage if they tumble.

Originally Posted by Soren

All im trying to say is that the 4x.303's + 2xHispano's armament wasnt ineffective, and more or less on par with the 2x.50's + 2xHispano's armament against Fighters.

Also the lower weight of the Browning .303 gun was an advantage of its own.

Well, I really don't think this is true. By mid war, against the FW190 the .303's were nearly useless. The combination of weak initial hitting power, poor ballistics, very poor hitting power at range, and small payload all added up to an ineffective round. And it was virtually impossible to make an API round in that caliber.

The only reason the British kept using the .303 was because they had to import the .50 BMG, but made their own .303 Brownings, along with the issues of adding .50 ammo to their supply chains. They were setup to support the .303, not the .50.

The .50 BMG was a very big improvement on the .303. The gap between .303 and .50 is much larger than the gap between .50 and 20mm.

Weighing less is only an advantage if the gun is still effective. The Soviet UBK Berezin was an example of a gun that was far more "efficient" than the .50 because it had the same hitting power but weighted a lot less (and had better RoF).

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Lunatic

[Soren]

RG if the .303 round can penetrate up to 9mm of steel at 200y, then it damn well wont peel off an "airframe" at that range !

So at 30-120m it is still lethal to any German Fighter !

Incidents where .303's rounds ricochet of German fighters, were incidents where the pilots have been a little to trigger-happy, firing at long range.

Tony's assessment is good enough for me:

4xBrowning .303's GunPower = 80

2xM2 .50's GunPower = 120

Originally Posted by Soren

RG if the .303 round can penetrate up to 9mm of steel at 200y, then it damn well wont peel off an "airframe" at that range !

That's at 0 degrees. Most strikes are going to be at high angles, typically 45-90 degrees. The penetration at 40 degrees is 4mm at 200 yards. At 60 degrees it would probably be about 2mm, if it penetrated at all. Punching through duraluminum at a 60 degree angle would leave very little energy for doing any damage.

Originally Posted by Soren

So at 30-120m it is still lethal to any German Fighter !

Enough of them yes. But against an FW, it would be an awful lot.

Originally Posted by Soren

Incidents where .303's rounds ricochet of German fighters, were incidents where the pilots have been a little to trigger-happy, firing at long range.

Sometimes. But they were also rounds that hit at 75 to 90 degrees off the normal (perpendicular) to the planes skin, or that hit at a lesser angle but hit where there was structure immeadiately under the skin.

Originally Posted by Soren

Tony's assessment is good enough for me:

4xBrowning .303's GunPower = 80

2xM2 .50's GunPower = 120

Well, maybe you should buy Tony's book, "FLYING GUNS OF WORLD WAR II", which clearly indictes that the .303's were simply too weak to be effective. In 1932-34 British studies determined that it would take 8 x .303's to deliver a lethal dose in two seconds of fire to existing fighters - that's 300 rounds, and it assumes a very high hit percentage.

On his website Tony also says:

Tests by the RAF indicated that both the .303 and 7.92mm AP bullets had some problems penetrating the structure of the relatively small and light Blenheim bomber. Both guns were fired at a range of 200 yards (180m) through the rear fuselage at the 4 mm armour plate protecting the rear gunner, which was angled at 60º to the line of fire. The results were poor; only 33% of the .303" rounds reached the armour (the rest being deflected or absorbed by the structure) and 6% penetrated it. In contrast, only 23% of the 7.92 mm bullets reached the armour, and just 1% penetrated

The incendiary ammunition was also variable in performance. Comparative British tests of British .303" and German 7.92 mm incendiary ammunition against the self-sealing wing tanks in the Blenheim, also fired from 200 yards (180m) astern, revealed that the .303" B. Mk IV incendiary tracer (based on the First World War Buckingham design – it was ignited on firing and burned on its way to the target) and the 7.92 mm were about equal, each setting the tanks alight with about one in ten shots fired. The B. Mk VI 'De Wilde' incendiary (named after the original Belgian inventor but in fact completely redesigned by Major Dixon), which contained 0.5 grams of SR 365 (a composition including barium nitrate which ignited on impact with the target) was twice as effective as these, scoring one in five.
http://www.quarry.nildram.co.uk/BoB.htm

And in his forums Tony says:

The FN-built version of the Browning did 1,400 rpm (they actually pushed it to 1,900 rpm, but decided that it wore out and broke too fast). However, that wouldn't make a major difference.

There was nothing that could be done to improve the ammo. The B Mk VII incendiary was as good as rifle-calibre incendiaries got, and the AP could only have been improved by using a tungsten carbide core.

Put simply, the round was too weak to be effective (except occasionally by chance) against the toughened-up aircraft which started to appear in mid/late 1940. The BoB was its finest moment, it was all downhill from then.
http://forums.delphiforums.com/autog...ges?msg=1705.2

And from E. Gustin's site (Tony's Co-Author for Flying Guns):

Phase I

In the first phase the rifle-calibre machinegun was still important. Fighters either carried a homogenous armament of such guns, or they used a mixture of rifle-calibre guns with cannon or medium-calibre machineguns. Examples of the first approach are the eight Browning .303s in the Spitfire and the four MG 17s in the early Fw 190. Examples of the second approach are the MG FF and MG 17 weapons of the Bf 109E, the two .50 and four .303 Brownings of the early P-51, or the two 20mm cannon and two 7.7mm guns in the A6M2. This first phase ended when it was understood that the rifle-calibre machinegun was ineffective against modern combat aircraft.

Light machineguns would put a lot of holes in the skin of an aircraft, but they could not cause it to break up. Therefore one aimed for the vulnerable, critical parts of the aircraft: The pilot, the fuel tanks, and the engines. However, armour and self-sealing fuel tanks were an effective defense. Many fighters entered the war without these items, but by 1941 a fighter without them was no longer considered suitable for combat.
http://www.geocities.com/CapeCanaver...n/fgun-an.html

So as you can see, Tony does not consider the .303 would have been effective even if the number of guns had been increased to 12 or the RoF increased to 1500 rpm!

Another point to be made is that the .303's ballistics differed so greatly from those of the Hispano that they really didn't work together. If you were scoring with one you were almost surely missing with the other, except at point blank (closer than 50 meters) range. .50 ballistics are fairly close to Hispano ballistics.

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Lunatic

[Soren]

Well you said the .303's would ricochet off the airframe, but they wouldnt, only if they hit a structured part. Also incendiary ammunition burns its way through instead, virtually neglating any slant.

The problem with the .303's and .50's were that they made relatively small holes, and only the .50's could do any real internal damage to any structured part.

But still the .303's werent ineffective, as they could still cut chords, and varius other things after penning the airframe.

Btw as a little side-note: The 7.92mm AP used in Tony's mentioned test, wasnt German ammunition but British built ammunition. The Germans used hotter loads for their 7.92mm ammunition, and sometimes a Tungsten core in the AP projectile, depending on the type.

So now Tony's opinion is not good enough for you?

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The incendiary did not burn its way through the skin of the plane. If it burst on the skin of the plane, it was wasted and blew away.

The USN did a test against self sealing fuel tanks using AP ammo. The .30 rounds punched a .3 inch hole in the top of the tank, and sometimes made a small exit hole in the bottom of the tank and sometimes remained in the tank - in either case the holes sealed. The .50's punched a .5 inch hole in the top of the tank, and made a 4 inch by 8 inch exit hole in the bottom which could not seal. The 20mm made a 20mm hole in the top of the tank..... and blew the bottom of the tank off at the seams!

As for the German 7.92mm ammo...



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Lunatic

[Soren]

The incendiary did not burn its way through the skin of the plane.

What ?!

From Tony's site: incendiaries burn on their passage through the target, setting light to anything inflammable they meet on the way.

You were saying ?

The USN did a test against self sealing fuel tanks using AP ammo. The .30 rounds punched a .3 inch hole in the top of the tank, and sometimes made a small exit hole in the bottom of the tank and sometimes remained in the tank - in either case the holes sealed. The .50's punched a .5 inch hole in the top of the tank, and made a 4 inch by 8 inch exit hole in the bottom which could not seal. The 20mm made a 20mm hole in the top of the tank..... and blew the bottom of the tank off at the seams!

Doesnt really correspond that well with previus quoted British tests though, now does it ?

As for the German 7.92mm ammo...

Thats an S.m.K. round, not an S.m.K.H round, but even this one penetrates 3mm of armor plating at 80* from vertical.

Originally Posted by Soren

What ?!

From Tony's site: incendiaries burn on their passage through the target, setting light to anything inflammable they meet on the way.

You were saying ?

I was saying if the incendiary expends on the skin, it won't burn through the skin. Also, Tony's description of how the incendiary works is just flat wrong. For the De'Wilde and M1 Incendiary, or the M8 API, the incendiary normally will not ignite on contact with the planes skin, but will ignite on contact with the next metal surface. When it does ignite, it will then ignite flamables that are contacted as it passes through the target.

If it should ingite on hitting the skin of the target this means something very solid lies beneath the skin or the angle is very oblique (and then it would usually ricochette). If this happens, the round will burst on the skin of the plane, making a visible flash but then the incendiary will probably blow away and do little damage.

In any case, the nature of the incendiary is such that it will not aid in penetration no matter what. By the time its transfered any significant heat, the metal of the round is long gone.

Originally Posted by Soren

Doesnt really correspond that well with previus quoted British tests though, now does it ?

British tests did not setup a self sealing tank half full of water and fire the round down into it from relatively close range. But British tests drew the same overall conclusion - the .303 was relatively ineffective against self sealing fuel tanks, and the 20mm and .50 were about equal.

Originally Posted by Soren

Thats an S.m.K. round, not an S.m.K.H round, but even this one penetrates 3mm of armor plating at 80* from vertical.

Not sure how you're reading it. In this chart, 90 is perpendicular to the plate. The largest angle shown is 30 degrees, which would be 60 degrees off the perpendicular using 0 as the normal.

Yes, the German 7.9 mm AP ammo was better than the British - the British incendiaries were better than the German.

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Lunatic

[Soren]

.303 incendiaries were reasonably effective agaisnt self sealing fuel tanks, but the .50's were better in the fact that it wouldnt take as many hits to rupture the tank.

Also, Tony's description of how the incendiary works is just flat wrong.

I'll let Tony defend that, but thats what every other source tells me aswell.

Not sure how you're reading it. In this chart, 90 is perpendicular to the plate. The largest angle shown is 30 degrees, which would be 60 degrees off the perpendicular using 0 as the normal.

As I said "80* from vertical", Vertical normally means 90*.

Above shows the S.m.K. rounds hitting a plate with a slant of 80* from vertical. (Or 20 degree's to Vertical)

Yes, the German 7.9 mm AP ammo was better than the British - the British incendiaries were better than the German.

Agreed.

[Soren]

Originally Posted by RG_Lunatic

Again, what I have to wonder is who wins the expected engagement. The P-51 and Spitfire are cruising at 30,000 feet. The P-51 is making 400 mph, and has pleanty of fuel to do so. The Spitfire is making 300 mph, and is pushing his fuel supply to do so. Can the Spitfire make up a 100 mph speed deficit?

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Lunatic

The Spit XIV's cruising speed was 362 mph, while the P-51D's was 275 mph. And why would they meet at 30,000ft ? Why not 15,000 or 10,000 ?

There's no question who's going to win the fight if both pilots are equal.
Not only is the Spit XIV more maneuverable at all altitudes, but it is faster, climbs better, thus it controls the whole engagement. The P-51 can't run once they've met, and by then the P-51 is dead meat, as the spit will be behind it in seconds !

The P-51's only chance is for it to get into a steep dive, and build up some speed, thus it has a small chance of escaping.

Originally Posted by Soren

The Spit XIV's cruising speed was 362 mph, while the P-51D's was 275 mph. And why would they meet at 30,000ft ? Why not 15,000 or 10,000 ?

You have those cruising speeds backwards.

At all altitudes the P-51 cruise is faster than the Spitfires. But the expected engagement would be at high altitude.

Originally Posted by Soren

There's no question who's going to win the fight if both pilots are equal.
Not only is the Spit XIV more maneuverable at all altitudes, but it is faster, climbs better, thus it controls the whole engagement. The P-51 can't run once they've met, and by then the P-51 is dead meat, as the spit will be behind it in seconds !

The P-51 turns and rolls better at very high speeds. The P-51 dives faster at a moderate dive angle. And the P-51 can sustain high speeds much longer. But I agree the P-51 would have to execute hit-and-run tactics against the Spit XIV, if it turns it's dead.

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Lunatic

[Soren]

You have those cruising speeds backwards.

At all altitudes the P-51 cruise is faster than the Spitfires.

Every single source on the P-51D and Spitfire that I have read, give the stats for the two aircraft that i just presented. 275 mph for the P-51D and 362 mph for the Spit XIV.

Think about it... the Spit XIV is lighter, has more prop-blades, its got a 2050 hp engine vs the P-51 wich is heavier and only has a 1475 hp engine.

But the expected engagement would be at high altitude.

Where the Spit still it at an advantage.

The P-51 turns and rolls better at very high speeds.

Correction, it ONLY roll better, it NEVER turns better ! Remember how stiff the P-51's elevators would get with speed ?

The P-51 dives faster at a moderate dive angle.

That is true.

And the P-51 can sustain high speeds much longer.

And what do you base that on ? The SPit can cruise at 362 mph, wich is only 40 mph away from the P-51D's "top speed".

But I agree the P-51 would have to execute hit-and-run tactics against the Spit XIV.

Wich it can't, as the Spit is noticably faster. Hey the XIV used to catch V1's !

I've proven in past posts the P-51 cruise speeds, which include up to 425 mph continues cruise at 30,000 feet.

I've not seen anything showing a cruise speed for the Spit XIV nearly as high as you claim. Cruise speeds I've seen listed typically run from 275-300 mph. The PR.XIX, a specialized high alt recon version could cruise at 370mph (595km/h) at 40000ft.

Originally Posted by Soren

Think about it... the Spit XIV is lighter, has more prop-blades, its got a 2050 hp engine vs the P-51 wich is heavier and only has a 1475 hp engine.

The V-1650-7 Packard Merlin was rated at 1695 hp at +18 lbs boost, about 1750 HP at +25 lbs boost. Then you have to addin the radiator thrust, worth about 300 HP at 400 mph TAS at 25,000 feet. The Spit XIV lacked sufficient cooling to sustain high level speeds for extended periods, once the bounadry layer starts seperating, the cooling system is not very efficient and creates tremendous drag.

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Lunatic

[Soren]

I've proven in past posts the P-51 cruise speeds, which include up to 425 mph continues cruise at 30,000 feet.

425 mph cruise speed ??!! You've got to be kidding me !

Read this, wich is exactly the same info you'll get from books about the P-51: http://www.wpafb.af.mil/museum/air_power/ap9.htm

I've not seen anything showing a cruise speed for the Spit XIV nearly as high as you claim. Cruise speeds I've seen listed typically run from 275-300 mph. The PR.XIX, a specialized high alt recon version could cruise at 370mph (595km/h) at 40000ft.

Well then you havent read much ! Read this:
http://www.xs4all.nl/~fbonne/warbird...#supespitfire3

The V-1650-7 Packard Merlin was rated at 1695 hp at +18 lbs boost,

Yes your right it was 1695 hp, an error on my side.

about 1750 HP at +25 lbs boost. Then you have to addin the radiator thrust, worth about 300 HP at 400 mph TAS at 25,000 feet. The Spit XIV lacked sufficient cooling to sustain high level speeds for extended periods, once the bounadry layer starts seperating, the cooling system is not very efficient and creates tremendous drag.

Well the Spit can maintain high speed flight long enough to get behind that P-51 and Shoot it down, wich is what matters.

Originally Posted by Soren

425 mph cruise speed ??!! You've got to be kidding me !

No I am not. Look at the P-51D/K pilot handbook flight ops chart for yourself:



I've highlighted the 425 mph cruise spec for you in blue. Note that this spec is a little off, as it shows an 870 mile range, but this is based upon the 23 gallons of fuel required to takeoff and climb to 10,000 feet. According to the chart on the previous page, it would take about 50-53 gallons to reach 30,000 feet (the chart only goes to 25K which takes 43 gallons), so actual range would be reduced accordingly.

Originally Posted by Soren

Read this, wich is exactly the same info you'll get from books about the P-51: http://www.wpafb.af.mil/museum/air_power/ap9.htm

Which gives you one of the many cruise options. I bet if it gives a range and altitude you can index it on the chart above and find they match exactly.

Originally Posted by Soren

Well then you havent read much ! Read this:
http://www.xs4all.nl/~fbonne/warbird...#supespitfire3

Come on! Give me a primary source document supporting this cruise speed, or at least a reputable source, not a warbirds fan site. If you check the Fourth-Fighter Group pages, it says max sustainable cruise of the Spit XIV was 300 mph.

Originally Posted by Soren

Yes your right it was 1695 hp, an error on my side.

No problemo.

Originally Posted by Soren

Well the Spit can maintain high speed flight long enough to get behind that P-51 and Shoot it down, wich is what matters.

If it can overcome the 100+ mph initial speed advantage of the P-51.

Also, you claim the Spitfire could out-turn the P-51 even at high speeds. It is true it does have a tighter minimum turning radius, but this is kind of irrelevant given that G forces will prevent the pilot from exploiting it. In a very high speed turn the pilot is the limitation, and the P-51 will loose less energy in the minimum turn the pilot can sustain, allowing him to work his way around behind the Spit unless the Spit sacrifices energy to slow down and tighten the turn... and we all know where that leads.

A little side note. In my debate on this topic someone on this board (through private msgs) claimed there was no real difference between the P-51B's and the P-51D's cruise performance, that they just found the P-51 could run at FT in the lean condition and revised the charts. I researched this and found it was not true.

In 1943 and early 1944 at the NACA Glenn research center a new fuel nozzle was developed which greatly increased the "fuel horspower" of an engine. This was applied to the P-51D/K first, starting in late-spring 1944, and then to the P-39/63 and Merlin powered Spitfires after P-51 demand could be fully met. Strangly, it seems not to have been applied to the R2800 powered US fighters, or the Napier Saber for that matter, until possibly after the war. I suspect scaling it up and tooling for production were a major undertaking.

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Lunatic